1. Field of the Invention
This invention relates generally to seals, and more specifically to a flexible sheet seal.
2. Description of the Prior Art
It is known in the art to join spaced apart members such as a pickup cap to a vehicle cab by a waterproof and airtight seal in the form of an inflatable doughnut. The doughtnut is positioned between facing cap and cab surfaces which are normally spaced two to five inches apart. The doughnut, when inflated, bears against the facing surfaces to provide a flexible seal therebetween. A disadvantage of the doughnut seal is that it relies on contact pressure rather than a positive connection, and hence an effective waterproof and airtight seal may not be secured. In addition, the doughnut seal requires attention and maintenance in regard to replacement of air valves, maintaining proper inflation pressure and locating and correcting air leaks as they develop. In the latter case, the seal is temporarily broken causing water and air leakage to occur. Another disadvantage of the doughnut seal is that the rubbing contact between the doughnut surface and the facing surfaces of the cap and cab causes abrasion of the paint on such surfaces resulting in an unsightly appearance. Such rubbing may also cause air leaks in the doughnut. A further disadvantage is that the doughnut seal has a tendency to slip out of sealing position causing water and air leaks to develop. Lastly, the doughnut seal must be slightly deflated while traveling through higher elevations. If this is not done, the reduced ambient pressure may cause the seal to rupture.
It is further known in the prior art to provide a seal between a cap and cab comprising an elongated fin-type strip preferably mounted on the front of the cap. The seal is achieved by butting the fin-type strip against a surface of the cab. This type of seal appears to operate satisfactorily if the cap and cab are tightly butted together, and no relative movement occurs between the cap and cab. Since relative movement between cap and cab occurs most of the time the vehicle is in motion, this is normally accompanied by water and air leakage through the seal.
Another disadvantage of the fin-type strip is that it hardens when the weather is cold, particularly during the winter months. This reduces the flexibility of the strip during relative movement between the cap and cab resulting in a less efficient seal and possible water and air leakage into the cap. Since a fin-type strip seal only works satisfactorily when a relatively close and parallel fit exists between the cap and cab, a cap equipped with such a seal may not be readily interchangeable on different vehicle cabs where the relatively close and parallel fit does not exist. Also, the fin-type strip seal is normally glued or screwed onto the support surface of the cap or cab resulting in an installation which is both time consuming and costly.
It is further known in the prior art to provide a channel-shaped sealing strip, of which U.S. Pat. No. 4,114,320 is exemplary. The sealing strip is mountable on a flange around a door or window opening in a motor vehicle body to prevent water and air leakage into the body. The sealing strip has gripping means by which the strip is mounted on the flange. The gripping means comprises gripping ribs extending longitudinally along the inside surface of the channel and projecting toward each other from the opposite side walls thereof. The rib on one wall is made of a relatively hard flexible material whereas the rib on the opposite wall is made of a relatively softer flexible material.